1. Field of the Invention
This invention relates to an image measuring apparatus and an image measuring method for photographing right and left images with a camera attached to an electron microscope or an optical microscope as a photographing device by tilting an observing object or dividing or tilting a beam such as an electron beam or a light beam to observe the observing object and performing two- or three-dimensional measurement of the object photographed in the right and left images.
2. Description of the Related Art
In the case of a transmission electron microscope (TEM), the sample is tilted to obtain transmission images at different tilt angles, and stereo observation is performed using the images as right and left images. In the case of a scanning electron microscope (SEM), the sample or the electron beam is tilted to obtain reflection images at different tilt angles, and stereo observation is performed using the images as right and left images as described in Medical and Biological Electron Microscopy (pp. 278-299, published in 1982). In the field of semiconductor producing equipment, JP-A-2002-270126 and 270127 disclose an electron beam device and a data processing device for an electron beam device capable of appropriately processing stereoscopic detection data obtained from an electron microscope to permit precise three-dimensional observation of an image of a sample and performing three-dimensional shape measurement of the sample based on the observation.
In measuring a sample such as a semiconductor chip or a silicone wafer, however, the measurement accuracy varies depending upon the measuring direction in some data processing method for three-dimensional shape measurement. In general, the projections or depressions, or the wiring pattern formed on a semiconductor chip or a silicon wafer includes many lines extending in the in-plane horizontal and vertical directions. In the stereo observation method using right and left images described in the above patent documents, the incident angle of the electron beam of the electron microscope is changed by rotating a semiconductor chip as an observing object about the holder rotation axis or tilting the electron beam so that right and left images of the semiconductor chip can be obtained. In some three-dimensional shape measurement, a sensitive axis extends in an in-plane direction perpendicular to the holder rotation axis direction (for example, a vertical pattern direction of the semiconductor chip as an observing object) and an insensitive axis without measurement sensitivity extends in the same direction as the holder rotation axis direction (for example, a horizontal pattern direction of the semiconductor chip as an observing object). Thus, although accurate measurement can be made in the direction of the sensitive axis, measurement cannot be made in the direction of the insensitive even if right and left images of the semiconductor chip are used. The three-dimensional shape measuring method having a sensitive axis and an insensitive axis will be hereinafter referred to as “anisotropic shape measurement”.
A semiconductor chip or a silicon wafer has a surface having projections or depressions (in the out-of-plane direction) formed by etching or multilayer wiring. The thickness distribution of the projections or depressions also has to be measured accurately. FIG. 26 is an explanatory view of right and left images of a semiconductor chip or silicon wafer having a surface with a projection. A surface of semiconductor chip or a silicon wafer has projections or depressions formed by etching, chemical vapor deposition (CVD), or spattering. The inclinations of the projections or depressions in the thickness direction thereof are large. Thus, in the case of parallel projection, some of slopes cannot be captured in one of the right and left images because of their inclination angle even if it is captured in the other. In this case, corresponding points of the slopes cannot be determined even if the right and left images are used, so that the three-dimensional shape measuring apparatus cannot measure the surface shape in the out-of-plane direction accurately.
This invention has been made to solve the above problem, and the first object of this invention is to provide a three-dimensional coordinate measuring apparatus and a three-dimensional coordinate measuring method which does not show no significant differences in measurement accuracy depending upon the measurement direction even in three-dimensional shape measurement using anisotropic shape measurement in which measuring accuracy varies depending upon the measurement direction. The second object of this invention is to provide a three-dimensional coordinate measuring apparatus and a three-dimensional coordinate measuring method capable of measuring the dimensions of the rises and falls in the out-of-plane directions on a surface of the object.